Material for electrophotographic purposes



United States Patent Office 3,180,730 Patented Apr. 27, 1965 3,180,730 MATERIAL FOR ELECT ROPHOTOGRAPHIC PURPOSES K 37, 36 32 Claim (Cl. 96-1) Electrophotographic material normally consists of a support on which there is a photoconductive substance, this coating being electrostatically charged in the absence of light. The material is then exposed to light behind a master, or an episcopic image is projected thereon, so that an electrostatic image is formed which corresponds to the master. This image is developed by being briefly contacted with a resin powder whereupon a visible image is formed which is fixed by heating, or by the action of solvents. In this way, an image of the master which is resistant to abrasion is obtained clectrophotographically.

For the photoconduetive coatings, inorganic substances such as selenium, sulphur or zinc oxide have been used and also organic compounds such as anthraccne and anthraquinone.

A material for electrophotographie purposes, consisting of a support and a photoconductlve coating, has now been found which is characterized in that the photoconductive coating consists of or contains at least one triphenyl amine compound which may have substituents on one or more of the phenyl nuclei.

The base materials used as supports may be any that satisfy the requirements of xcrography, e.g. metal or glass plates, paper or plates or foils made of electroconductivc resins or plastics, such as polyvinyl alcohol, polyamldes, and polyurethanes. Other plastics which have the required electroconductlve properties, such as cellulose acetate and cellulose butyrate, especially in a partially saponilled form. polyesters, polycarbonates, and polyoleiincs, if they are covered with an elcctroconductive layer or if they are converted into ciectroconductive materials c.g. by chemical treatment or by the introduction of matcrials which render them clcctroconductlve, may also be used. Generally, elcctroconductive supports are suitable for the purposes of the present invention. in the sense of the present invention the term "electroconductive support" comprises materials having a specific conductivity higher than l'""ohm".cm.- preferably higher than l0 ohm- .cm.

it paper is to be used as supporting material, it is preterably pretreated against the penetration of the coating solutions, e.g. it can be treated with a solution of methyl cellulose or polyvinyl alcohol in water or with a solution of an lnterpoiymer of acrylic acid methyl ester and aerylonitriie in a mixture of acetone and methylethyl kctone, or with solutions of polyamides in aqueous alcohols, or with dispersions of such compounds.

According to the present invention triphenylamine and its substitution products are the compounds used as photoconductlve coatings. Even unsubstituted triphenylamine is effective, but the sensitivity of the photoconductive coatings can be increased if the triphenylamine compounds have substituents in one or more of the phenyl nuclei; the substituents can be in the o, m, or p-positlon to the amine nitrogen.

A particularly good effect is obtained, however, if the substituents are in the para position to the nitrogen atom. Suitable substituents are amino groups, alkylamino groups such as dimethylamino, diethylamino and dlpropylamino groups, and also amino groups that are merely alltylatcd (ill such as methylamino, ethylamino and propylamino groups. Similarly, the phenyl radicals can be substituted by acylamlno groups, particularly of lower fatty acids such as acetic acid, propionic acid or butyric acid, by lower alkyl groups such as methyl ethyl, propyl, butyl and amyl groups, lower alkoxy groups such as methoxy, cthoxy, propoxy or butoxy groups, or by halogens such as chlorine, bromine and iodine, or nitro or nitriie groups. In general, it can be said that any substituents may be employed which are inert at the conditions under which electrocopying material is used, do not increase electrical conductivity to any appreciable extent, and have no active hydrogen. Acid substituents such as SO H, COOH or those which are affected by moisture such as COCl, -S0,Cl or --COO-alkyl are therefore excluded. Exemplary triphenylamincs are the following:

Formula I Formula 2 Q-N-G-NIIO 0cm Formula 3 Formula 4 Formula 5 Formula 6 Formula 7 Formula 8 Formula 9 Formula I 0 Formula II Formula I2 llr Formula 13 t-amlno-trlphenylnmlne, 4-acetamino-trlphcnylamine, 4-dimethylamino-triphenylamlne, t-methoxy-triphenylnmine, t-ethoxy-trlphenylamine, 4-methyl-trlphenylamine, 3-methyi-trlphcnylnmlne, Z-methyl-triphenylnmine, t-chlor-triphenylamine, 4-nitro-triphcnylnminc, .i-methyl-4'-nitro-trlphcnylamlne, 4,4,4"-tribromtriphenylamine.

supporting material is coated with the solution in the normat manner, e.g. by immersion processes, painting, roller application or by spraying. The material is then heated so that the solvent is removed. A number of the triphenylamines mentioned can be applied together to the supporting material or the compounds can be applied in association with other photoconduetive substances.

Further, it is often advantageous for the triphcnylamines to be used as photoconductivc coatings in association with organic resins. Resins primarily of interest for this purpose include natural resins such as balsam resins, colophony and shellac, synthetic resins such as phenol resins modified with colophony, and other resins in which colophony constitutes the major part, coumarone resins, indene resins and those included under the collective term "synthetic lacquer resins." According to the Saechtling-Zebrowski Plastics Handbook Kunststolltaschenhuch, llth edition, 1955, page 2l2 ct scq., these include the following: processed natural substances such as cellulose cthers; polymers such as vinyl polymers, c.g., polyvinyl chloride, polyvinylidcnc chloride, polyvinyl acetate, polyvinyl ncetals, polyvinyl cthers, polyacrylic and polymcthacrylie acid esters, as also polystyrene and isobutylcnc and chlorinated rubber; polycondensatcs, c.g., polyesters, such as phthalate resin, alkyd resin, maleic resinate, maleic acid-colophony mixed esters of higher alcohols, also phenol-formaldehyde resin, in particular colophony-modified phenol-formaldehyde condensates, urea-formaldehyde condensates, melamine-formaldehyde resins, aldehyde resins, kctone resins, particularly so-called AW 2 resins. xylene-formaldehyde resins, polyamldes, polyadducts such as polyurethanes. Also, polyolcfincs such as various polyethylenes, polypropylencs and phtalic acid polyesters such as terephthalic and isophthalic acid ethylene glycol polyesters may be used.

if the trlphenyinmines are used in association with the resins described above, the proportion of resin to photoconductive substance can vary very greatly, but the content of photoconductive substance should be at least 20%. Mixtures of front 2 parts of resin and one part of photoocnductivc substance to one part of resin to two parts of photoconductive substance are to he preferred. Mixtures of the two substances in equal parts by weight are particularly favorable.

The solutions of the triphenyiamines. with or without the resins, are applied to the supports in the usual manner, for example by painting, rollerapplication, immersion or spraying, and then dried, an even, homogeneous, transparent and, in most cases, colorless photocondnctive layer being thus formed. The light-sensitivity of these photoconductive coatings is in the long-wave ultraviolet region, at about 3600-4200 A. With mercury vapor lamps, which transmit a large amount of ultraviolet rays, short exposure times can be achieved.

The light sensitivity of the photoconductive layer in the visible part of the spectrum can be highly improved by the addition of sensltizers so that even with normal light sources short exposure times can be achieved. Even very small additions, e.g. less titan 0.01 percent, have considerable effect. In general, however, the amount of "sensltlzer" to be added to the photoconductive substance is from 0.01 to 5 percent and preferably 0.1 to 3 percent. The addition of larger quantities of sensitizer is possible but in general is not accompanied by any considerable increase in sensitivity.

Suitable sensitizers are con tituted in particular by dyestuffs. such as those listed by way of example below. They are taken from Schultz Farbstofftabellcn." 7th edition. 1931. 1st vol.

Triaryimcthane dyestuffs such as Brilliant Green (No. 760, p. 314), Victoria Blue 8 (No. 822, p. 347). Methyl Violet (No. 783, p. 327). Crystal Violet (No. 785. p. 37.9). Acid Violet 68 (No. 83i. p. 35l); xanthene dyestuffs. namely rhodamines. such as Rhodamine B (No. 864. p. 365). Rhodamine 66 (No. 866, p. 366). Rhodamine Extra (No. 865. p. 366). Sulphorhodan'tinc B (No. 863. p. 364) and Fast Acid Eosin G (No. 870, p. 368). as also phthaieins such as Eosin S (No. 883, p. 375). Eosin A (No. 88l, p. 374). Erythrosin (No. 886. p. 376). Phioxin (N0. 890, p. 378). Bengal Rose (No. 889. p. 378). and Fluorcsccin (No. 880. p. 373); thiazinc dyestuffs such as Methylene Blue (No. 1038, p. 449); acridine dyestuffs such as Acridine Yellow (No. 90f. p. 383). Acridine Orangt (No. 908. p. 387) and Trypaflavine (No. 906. p. 386); quinoline dyestuffs such as Pinacyanol (No. 924. p. 396) and Cryptocyaninc (No. 927. p. 397); quinone dyestuffs and ltetone dyestuffs such as Aliznrin (No. li4l. p. 499). Alizarin Red S (No. H45. p. 502). and Quinizarine (No. i148, p. 504); cyanine dyestuffs. e.g. Cyaninc (No. 921, p. 394) and chlorophyll.

For the production of copies. the photocoaductivc coating is charged positively or negatively by means of. for example. a corona discharge with a charging apparatus maintained at 6000-7000 volts. The electrocopying material is then exposed to light in contact with a master. Alternatively. an episcopic or diaseopie image is projectcd thereon. An electrostatic image corresponding to the master is thus produced on the material. this invisible image being developed by contact with a developer consisting of carrier and toner. The carriers used may be. for example. tiny glass bails. iron powder or tiny plastic balls. The toner consists of a resin-carbon black mixture or a pigmented resin. The toner is generally used in a grain size of l to 100 preferably to a. The developer may also consist of a resin or pigment susended in a non-conductive liquid. in which resins may be dissolved. The image that now becomes visible is then fixed. e.g.. by heating with an infra-red radiator to l00l70 C.. preferably l20-l50' C.. or by treatment with solvents such as trichloroethyicne. carbon tetrachloride or ethyl alcohol. or steam. if a polarity of the electrical charge is used which is opposite to that of the toner contained in the developer, images corresponding to the master characterized by good contrast effect are obtained. fly changing the polarity of the corona discharge it is thus possible to obtain reversal images with the same master and the same toner.

The clcctrophotographlc images thus obtained can be converted into printing plates. it the support. e.g., paper. metal or plastic foil. is wiped over with a solvent for the photoconductive layer. e.g. alcohol or acetic acid. then rinsed with water and inked up in known manner with greasy ink. in this manner. printing plates are obtained which can be set up in an offset machine and used for printing.

it transparent supporting material is used. the electrophotographic images can also be used as masters for the production of additional copies on any type of lightsensitive sheets. in this respect. the photoconductive compounds to be used as provided by the invention are superior to the substances used hitherto, such as selenium or zinc oxide. inasmuch as the latter give only cloudy layers.

The photoconductive layers of the Present invention can be charged positively as well as negatively. This has the advantage that with the same developer, merely by changing the polarity of the corona discharge. it is possible to obtain direct and reversal images from the same master. The photoconduetivity of the photoconductors according to the present invention is superior to that of known organic photoeonductive substances, such as anthracene, beazidine. and anthraquinone.

lf translucent supports are used for photoconductive layers such as are provided by the invention, images can be' produced by the reflex method also. The electrophotographic material of the invention has the advantage that it gives images rich in contrast and that it can be charged positively as well as negatively.

The preparation of the photoconductive substances is illustrated below by some examples:

4 dimethylamino triphcnylamine, corresponding to Formula 4. with a melting point of 125 C., is obtained if a solution of 5.2 parts by weight of 4-aminotriphenylamine, corresponding to Formula 2, and 4 parts by volume of dimethylsulphate in 30 parts by volume of ethyl alcohol is first shaken. then boiled, and then treated with 20 percent sodium hydroxide solution. The crude product. which separates out during cooling, is recrystallized from benzene.

4-cthoxy-triphcnylaminc. corresponding to Formula 6, with a melting point of 91 C., is obtained if a mixture of 17.6 parts by weight of diphcnyiamine, 24.8 parts by weight of p-iodophenetolc, 13.8 parts by weight of anhydrous potassium carbonate and 0.5 part by weight of copper powder is heated for 12 hours in 100 parts of volume of nitrobcnzene. The water formed during the reaction is removed from the reaction products as it is produced. The nitrobcnzene is then driven oil by steam distillation and the residue is extracted with ether and shaken with dilute hydrochloric acid and water. The ether extract is dried over calcium chloride. The ether is distilled off and the residue is purified by recrystallization from alcohol in the presence of animal charcoal.

Z-methyl-triphenyiamlne. corresponding to Formula 9. with a melting point of 60 C.. is obtained if a mixture of 13.6 parts by weight of diphenylamine, 17 parts by weight of o-iodo-toluene. 10.7 parts by weight of anhydrous potassium carbonate and 0.3 part by weight of copper powder is heated for 12 hours in parts by volume of nltrobenzcnc. Further procedure is as described above under Formula 6. The crude product is twice recrystallized from alcohol in the presence of animal charcoal.

3-mcthyl-4'-nitro-triphenylamine, corresponding to Formula 12, with a melting point of C., is obtained if a mixture of 23.5 parts by weight of 4-nltrotriphcnylamine, 22 parts by weight of m-iodo-tolucne, 13.8 parts by weight of anhydrous potassium carbonate and 0.5 part by weight of copper powder is boiled for 12 hours in 100 parts by volume of nitrobcnzene. Further procedure is as described above under Formula 6. The crude product is twice purified from alcohol in the presence of animal charcoal. The invention will be further illustrated by reference to the following specific examples:

Example I 1 part by weight of trlphcnylamlne. corresponding to Formula 1. and 1 part by weight of ltetone resin (Kunstharz EM) are dissolved in 30 parts by volume of glycol monomcthylcther. The solution is applied to a paper foil which in known manner has been made. by means of a prccoat. resistant to the penetration of organic solvents. After evaporation of the solvent. the coating adheres firmly to the surface of the paper.

On this paper. direct images are produced by the electrophotographic process in the following manner: the paper is given a negative electrostatic charge by corona discharge and is exposed under a master to the light of a high pressure mercury vapor lamp. It is then powdered over with a developer consisting of a mixture of carrier and toner. The carrier used may consist of, e.g., tiny glass balls or iron powder. The toner consists of a resincarbon black mixture or of a pigmented resin of a grain size of l to 100 n, preferably 5-30 a. The finely divided resin-carbon black mixture (toner) which due to triboelcctric effects acquires a positive charge adheres to the parts of the coating not struck by light during the exposure and an image corresponding to the master becomes visible. it is heated and thereby made permanent (fixed).

lly changing the polarity of the corona discharge, it is also possible to obtain reversal images, using the same toner and the same master.

if a suitable transparent plastic foil or transparent paper ("l-lartpost) is used as a support for the photoelectric coating instead of the paper used in the case described above, the images produced are suitable as reproduction masters for any sort of duplication by means of light-sensitive sheets.

Example 2 1 part by weight of 3-mcthyi-4'-nitrotripbenyiamine, corresponding to Formula 12, and 1 part by weight of kctone resin (Kunstharz SK) are dissolved in 30 parts by voittmc of glycol monomethylethcr and coated upon a superficially roughened aluminum foil. tion of the solvent. the coating remaining adheres firmly to the surface of the foil. For the preparation of an image, the further procedure is as described in Example 1. An image corresponding to the master is obtained which is fixed, similarly as described in Example 1. This image I:

can be converted into a printing plate if the aluminum foil is wiped over on the image side with a developer consisting of glycol monomcthylethcr and 1.5 percent phosphoric acid in the propottiont; of i: i; rinsed down with water and inked up with greasy ink and 0.5 percent phosi phoric acid.

Example 3 1 part by weight of 4-nmino-triphcnylaminc, corresponding to Formula 2, and 2 parts by weight of cou- Example 4 1 part by weight of triphenylamine, corresponding to Formula I, and 1 part by weight of kctone resin (Kanstharz EM) are dissolved in 30 parts by volume of glycol monomethylethcr; 0.01 pttrt by weight of Rhodaminc B (Schuitz "Farbstofl'tabcllen," 7th edition, lst voi., No. 864) is added to the solution, which is then coated upon a paper foil that has been made, by means of a prccottt, impermeable to organic solvents. After the evaporation of the solvent, the coating adheres firtnly to the surface of the paper foil. in a manner known per sc, the coated paper foil is provided with a positive electrostatic charge and, tints sensitized, is exposed under a master, c.g., for 1 second to the light of a 100 watt incandescent lamp at a distance of 15 cm., and then the exposed surface is dusted over with a developer consisting of a mixture of carrier and toner. The carrier used consists of, c.g., tiny glass bails, coated with a resin, e.g. coumarone resin. The toner consists of a carbon black-resin mixture or a pigmented resin of a grain size of i to iOO t, preferably S-IlO An image corresponding to the master is formed which is fixed by treatment with trichiorocthylene vapors.

Example 5 0.7 part by weight of triphcnylamlne, corresponding to Formula 1, 0.7 part by weight of 4-aminotriphcnyittmine, corresponding to Formula 3, and 0.7 part by weight of 4-dimethylamino-trlphenylamine, corresponding to Formttia 4. are dissolved in 30 parts by volume of toluene. About 15 parts by volume of this solution are coated upon a paper foil of size DIN A 4 the surface of which After cvapora- Kit) I.) has been treated against the penetration of organic solvents and the coating is dried. With the coated paper foil, electrophotographic images are produced as described in Example 1. if, after the image has been powdered over with the developer described in Example 1 but not yet fixed, a sheet of paper is placed thereon and the back of the transfer material is charged by means of a corona discharge, the charge having the same polarity as that originally applied to the eicctroconductive material before exposure, the carbon black-resin powder image will be transferred from the electrophotographic coating to the paper in the form of a mirror image. If the carbon blackresin image is transferred to transparent paper or to a transparent plastic foil, the image obtained can be further reproduced, e.g., on diazo paper.

Example 6 1 part by weight of 4-acctamino-triphenylamine, corresponding to Formula 3, 1 part by weight of a polymerizcd natural resin ("Poly Pale) and 0.01 part by weight of Acid Violet 6 EN (Schultz' Farbstofftabellen," 7th edition, ist voi., 193i, No. 831) are dissolved in 30 parts by volume of glycol monomethylethcr. The light blue solution is applied to paper and dried. After being charged by means of a corona discharge. the sensitized paper is exposed under a transparent master to a 100 watt incandescent lamp and dusted over with a developer consisting of a mixture of carrier and toner. The carrier used can be, e.g.. tiny glass halls, iron powder or organic and inorganic substances. The toner consists of a resin-carbon black mixture or a pigmented rcsin of a grain size of l to l00 t, preferably 540 An image corresponding to the master is formed which is fixed by heating. images rich in contrast and free of background are produced on light blue ground.

it will be obvious to those skilled in the art that many modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications.

What is claimed is:

l. An elcctrophotogrnphic material comprising a condactivc support layer and a photoconductivc insulating layer, the latter comprising a dyestufl sensitizcr and a compound selected front the group consisting of triphcnylaminc and a substituted triphcnyiamlne the substituents of which are inert at the conditions under which the material is used, do not increase electrical conductivity to a substantial extent, and contain no active hydrogen.

2. An electrophotographic material comprising a conductive support layer and a photoconductivc insulating layer, the latter comprising a dyestuff sensitizer and a compound selected from the group consisting of triphenyiamine and triphenylamine substituted by amino, alkylamino, ncylamino. lower aikyl, lower alkoxy. halogen, nitro, and nltriie radicals.

3. An electrophotographic material comprising a conductivc support layer and a photoconductivc insulating layer, the latter comprising tripltenylamine and a dyestuf'f sensltizer.

4. An eieetrophotographic material comprising a conductive support layer and a photoconductive insulating layer, the latter comprising a dyestuff sensltlzcr and a compound having the formula 5. An clcctrophotogrttphie material comprising a conlayer, the latter comprising a dyestuii sensitizer and a compound having the formula 6. An electrophotographic material comprising a conductive support layer and a photoeonductive insulating layer. the latter comprising a dyestuii' sensitizer and a compound having the formula lls 7. An electrophotographie material comprising a conductive support layer and a photoconductive insulating layer. the latter comprising a dyestuil sensitizer and a Compound having the formula O-N-O-OCH:

ll. An eicclropholographic material comprising a conductive support layer and a pholoconductive insulating layer. the latter comprising a dyestuil sensltizer and a compound having the formula 9. An eieclrophotographle material comprising a condtlctivc support layer and a photoeonductive insulating layer. the latter comprising a dyestull scnsltizer and a compound having the formula it). An eiectrophotegraphlc material com rising a conductive support layer and a photoconductve insulating layer. the latter comprising a dyestuil sensitlzer and a compound having the formula (iii;

it. An eieetrophotographlc material comprising a conductive support layer and a photoeonduetive insulating (iii Oil

layer, the latter comprising a dyestufi scnsitizcr and a compound having the formula 12. An eleetrophotographic material comprising a conduetive support layer and a photoconduclive insulating layer. the latter comprising a dyestutf sensitizer and a compound having the formula O-N-O-Cl 0 13. An eieelrophotographic material comprising a conductive support layer and a photoconductive insulating layer. the latter comprising a dyestufi' sensllizer and a compound having the formula 14. An electrophotographic material comprising a conductive support layer and a photoconduetive insulating layer, the latter comprising a dyestuil' sensitizer and a cotnpotmd having the formula Oil;

15. An electrophotographlc material comprising a conducllve support layer and a photoconductive insulating layer. the latter comprising a dyestuil sensitizer and a compound having the formula 16. A photographic reproduction process which comprises electrostaticaily charging a supported pholoeonductlve insulating layer. exposing the charged material to a light image and developing the resulting image with an electroseopie material, the photoconductlve layer comprising a compound selected from the group consisting of trlphenyiamine and a substituted triphenyiamine the substltuents of which are inert at the conditions under which the material is used. do not increase electrical conductivity to a substantial extent. and contain no active hydrogen.

l7. A photographic reproduction process which comprises eiectrostatlcaliy charging a supported photoconduetive insulating layer, exposing the charged material to a light image and developing the resulting image with an eleetroseopie material, the photoconductive layer comprising a compound selected from the group consisting of trlphenylamiae and triplteaylamlae substituted by amino. nlkyiamino. ncylamlno. lower alkyl, lower aikoxy, halogen. nitro, and nitrile radicals.

IR. A process according to claim 16 in which the pholoeonductive layer contains a resin.

I). A process according to claim i6 in which the photoconductive layer contains a sensitizer.

20. A photographic reproduction process which comprises cleetrostaticaliy charging a supported photoconduetive insulating layer. exposing the charged material to a light image and developing the resulting image with an eleetroseopie material, the photoeonductive layer comprising triphenylamine.

21. A photographic reproduction process which eomprises electrostaticaliy charging a supported photoconduetive insulating layer, exposing the charged material to a light image and developing the resulting image with an eiectroscopic material. the photoeonductive layer comprising a compound having the formula 22. A photographic reproduction process which comprises elcctrostalicnily charging a supported photoconduetive insulating layer. exposing the charged material to a light image and developing the resulting image with an clectroscopie material. the photoconductive layer contpridng a compound having the formula Cli 2d. A photographic reproduction process which comprises eieetrostatically charging a supported photoeonducthe insulating layer. exposing the charged material to a light image and developing the resulting image with an eiectrosenple material. the photoconductive layer comprising a compound having the formula 25. A photographic reproduction process which comprises eicctrostaticaliy charging a supported photoconduclive insulating layer. exposing the charged material to a light image and developing the resulting image with an clectroscopic material. the photoconduetive layer comprising a compound having the formula iii iii)

2 26. A photographic reproduction process which comprises electrostatieally charging a supported photoconduetive insulating layer, exposing the charged material to a light image and developing the resulting image with an electroscopie material, the photoconductive layer comprising a compound having the formula 27. A photographic reproduction process which comprises eleetrostatieally charging a supported photocopductive insulating layer. exposing the charged material to a light image and developing the resulting image with an eleetroscopic material. the photoconductive layer comprising a compound having the formula Oil:

28. A photographic reproduction process which comprises eiectrostatieally charging a supported photoconduetive insulating layer. exposing the charged material to a light image and developing the resulting image with an clectroscople material, the photoconductive layer comprising a compound having the formula Cll;

29. A photographic reproduction process which contprises eicctroslatieally charging a supported photoeonduetive insulating layer. exposing the charged material to a light image and developing the resulting image with an electroseopic material, the photoconduetive layer comprising a compound having the formula 30. A photographic reproduction process which comprises eiectrostatieaiiy charging a supported photoconduetive insulating layer. exposing the charged material to a light image and developing the resulting image with an electroseople material. the photoeonduetive layer comprising a compound having the formula 31. A photographic reproduction process which comprises eleetrostntlcaliy charging a supported photoconduetive insulating layer. exposing the charged material to a light image and developing the resulting image with 13 an electrosc pie material, the photoconductive layer comprising a compound having the formula 32. A photographic reproduction process which comprises eleetrostatically charging a supported photoconductive insulating layer. exposing the charged material to a light image and developing the resulting image with an elcctroscopic material, the photoconductive layer comprising a compound having the formula 1 4 References Cited by the Examiner UNITED STATES PATENTS 2,297,691 10/42 Carlson 96-1 2,766,233 10/56 Kartinosetal. "252-3012 5 3,042,515 7/62 Wainer 9690 FOREIGN PATENTS 562.336 5/58 Belgium. 10 1,177,936 12/58 France. 1,188,600 3/59 France.

201,301 3/56 Australia.

OTHER REFERENCES JACS 66, December 1944, pp. 2100-2116. Das Papier, April 1954, pp. 109-120. Vartanlan: Acts Phyalcochlmica URSS, vol. 22, #2, pp. 201-24, 1947.

Winslow ct 111.: IACS 77, Sept. 20, 1955, pp. 4751-6. Lyons et 81.: 1. Chem. Soc., 1957, pp. 3648-68.

NORMAN G. TORCHIN, Primary Examiner.

PHILIP E. MANGAN, Examiner. 

1. AN ELECTROPHOTOGRAPHIC MATERIAL COMPRISING A CONDUCTIVE SUPPORT LAYER AND A PHOTOCONDUCTIVE INSULATING LAYER, THE LATTER COMPRISING A DYESTUFF SENSITIZER AND A COMPOUND SELECTED FROM THE GROUP CONSISTING OF TRIPHENYLAMINE AND A SUBSTITUTED TRIPHENYLAMINE THE SUBSTITUENTS OF WHICH ARE INERT AT THE CONDITIONS UNDER WHICH THE MATERIAL IS USED, DO NOT INCREASE ELECTRICAL CONDUCTIVITY TO A SUBSTANTIAL EXTENT, AND CONTAIN NO ACTIVE HYDROGEN. 